U.K. Lab Says It Doesn't Know Nerve Agent's 'Precise Source,' Drawing Russian Retort

Scientists at a U.K. government laboratory have not verified the source of the substance used to poison Russian ex-spy Sergei Skripal and his daughter, Yulia, according to the lab's chief executive.

"We were able to identify it as novichok, to identify that it was a military-grade nerve agent. We have not verified the precise source," Gary Aitkenhead of the Defence Science and Technology Laboratory told British broadcaster Sky News on Tuesday. "But we provided the scientific information to the government, who have then used a number of other sources to piece together the conclusions they've come to."

Aitkenhead added that while his lab — better known as Porton Down after its secretive site in southern England — has been tasked with examining the chemical, "it's not our job to then see where it was actually manufactured." He only went so far as to note that the sample they studied is "probably only within the capabilities of a state actor."

Still, his reticence to confirm a specific source appears to undercut an account offered by Foreign Minister Boris Johnson, who spoke to German broadcaster Deutsche Welle amid the international dispute brewing over the attack. On March 20 — the same day the U.K. formally expelled 23 Russian diplomats for the Kremlin's alleged role in the Skripals' poisoning — Johnson told DW that researchers at the laboratory "were absolutely categorical" about the evidence.

"I mean, I asked the guy myself," Johnson said. "I said, 'Are you sure?' And he said, 'There is no doubt.' "

Opposition lawmakers in the U.K. quickly pointed out the discrepancy, including Labour MP Chris Williamson, who tweeted that Johnson had "just lied to justify our country's foreign policy."

But perhaps the more vehement response came from Russian officials, who have denied the allegations that the Kremlin was involved in the attack. They quickly pounced on Aitkenhead's comments, pointing to them as proof of what they have maintained all along — that the British claims, and those of their Western allies, are fabrications "part of a large-scale political provocation."

"We understood from the very start that UK Government statements on the nerve agent having been produced in Russia were a bluff. Now this has been confirmed by the head of the secret lab," the Russian Embassy in the U.K. said in a statement Tuesday. "This only proves that all political declarations on the Russian origin of the crime are nothing but assumptions not stemming from objective facts or the course of the investigation."

The Embassy also implied Porton Down was the actual source of the chemical: "Mr Aitkenhead is not denying that the lab had developed or keeps stocks of the agent they call 'novichok', although, of course, he would not admit it."

During his interview with Sky News, Aitkenhead addressed the suggestion that the nerve agent allegedly smeared on the Skripals' front door originated in his lab.

"There's no way that anything like that would ever have come from us or leave the four walls of our facility," he said. "We've got the highest levels of security and controls. We are regularly audited by the [Organisation for the Prohibition of Chemical Weapons] to make sure we're operating within those controls. And if there was any hint that anything we have would be leaving our four walls, then we wouldn't be allowed to operate."

The OPCW, the international chemical weapons watchdog, plans to hold a special session on the incident in the Hague on Wednesday. And Russian leaders are eager for it: They have already promised to raise a set of 13 questions at the meeting, pointed queries directed specifically at the British investigation into the incident.

For his part, one of the Russian chemists who developed novichok told NPR's Deborah Amos that "it's no secret" the Skripals were victims of a Russian assassination attempt.

The daughter, Yulia, has been "rapidly improving," according to the hospital treating her. Meanwhile, her father, Sergei, remains in critical condition.

"There's not — as far as we know — any antidote that you can use to negate the effects of it," Aitkenhead said of novichok. "We can, and we have, advised the hospital and the medics on the best course of trying to mitigate against the effects. But this is an extremely toxic substance and not something that you can easily give something to somebody to help them recover."

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